I'm presuming that the Idaida test will comprise straight line testing of aerodynamic components. This circuit has been frequently used for this purpose over the course of a number of seasons.

For Susie to be the first behind the wheel this test will have to take place prior to the launch of the Williams on February 19th which will coincide with the first day of testing at Barcelona. An opportunity for some enterprising (non-F1) photographer to get exclusive shots of the new car before it's launch.

What is not clear is exactly what her role is to be. No mention is made as to whether she is the de facto third driver and the press release from Williams is carefully worded to state that she will be continuing her role as Development Driver, but then goes on to make it clear that her role has been expanded significantly on last year's.

Susie, on her role at Williams states:

Increasing my role this year will further this progression (development as a driver) and I can’t wait to get behind the wheel of the FW35 for the first time next month. I’m showing that women can play a role at the top level of motorsport and would like to thank Sir Frank Williams and the whole of the technical team for the trust they continue to show in me.

Mike Coughlan's statement is where the obfuscation takes place:

Susie has proved herself to be a valuable addition to our driver roster and her feedback during simulator sessions is second to none. As a result we will be stepping up her role this year and I’m looking forward to the progress we can make with Susie’s input in conjunction with that of Pastor and Valtteri.

This is why I wonder whether she is given the step to Test Driver - her input in conjunction with Pastor and Valtteri - no mention is made of another driver who might provide input. This of course could be down to the fact that Williams have made no decision as of yet, however, it may well be that what is left unsaid may provide insight into the Williams frame of mind, no driver will be named and no commitment to Susie will be made in the form of Job Title. That plan would pave the way for the team to bring a third driver on-board should one be needed at a later date but will also allow both Team Drivers to partake fully in the FP sessions leading up to qualifying and the GP's throughout the 2013 season.